Hope this is the right place, feel free to move, just let me know where !

I was requested to cut a "Double Happiness" chinese symbol. (see enclosed files if you want it)

First, I had to review the phlatscript tutorial, as I couldn't make the inside cut tool work. Only when I saw that you had to fill holes by a face I managed to do what i wanted. A bit counter intuitive, but I understand it could make things easier on the software side.

Having just polished the Y rods and set up a new different computer to drive the phlatty (my HTPC with a startech PCI parallel card),

I decided to be daring and cut 6mm poplar plywood with a 1.5mm bit

I stopped it half way because there started to be a tiny bit of smoke coming out. (didn't really fancied a fire in the living room)
Still I consider it a half success, which should be able to become a full success soon.

I ran the printer at Y15, X15, Z10, and feed rate 10%, so very slow. Spindle at second setting out of 4. Maybe I should have reduced spindle speed even further.

I am not sure I care that much more about speed, it'll always be faster than me cutting it by hand.

I still have problem setting a correct Z home that will go through entirely, but not cut while travelling. for 6mm, Z out seemed to be 0.35 inch out.
Next time, I will first dry run to find out how much the bit should stick out, stop it, set the Dremel bit next to the material I want to cut, jog it to just above the thickness of the material, then Substract the max z value, and home it like that...

The rollers didn't slip, I think. Provided the end of the plywood was sliglty lifted (0.75 inch at the end of rear table)
The problem is that what i used to lift the plank up was a bit heavy, no too much but enough so the tape was starting to unstick out every 10 min... need a better solution. probably legs at the end.

The Y axis wobble I have due to Z axis play is amplified when cuttin hard materials... I seriously need to fix that.
I think I need to order a new gantry.
The problem is the 2 rods that guide the Z up and down don't fit very well in the top plate holes... Attached files Chinese_Symbol.zip (59.6 KB)Â

 

Are the 2 z rods too short? I replaced mine, first thing, because they were almost 1/4" short. So if you bottom out the rod on the bottom hole, there is not much left for the top. Is that what you mean? It's even worse if, you make the top removable. Because you can't even glue it anymore and have it removable. I have since torn up my y-axis and made the top removable; and my new rods still work very well.

I haven't finished the bushing mod, so I can't speak of the results. But I have confidence it's way better than the pex pipes. You should consider it, before ordering a new gantry. The only thing, is you have to move the holes slightly.

The wood looks burnt?

-Kwok

 

hey kwok,
no, the 2 z rods are not short... the right one, looking from the front of the phlatprinter fits fine, but the left one (away from the board) doens't to fit very well in the hole . the top of the rod is a bit too much too the left.

when the gantry moves up, it is not a uniform movement, it swing left-right, left right. I will try to post a video soon.

the closer it comes to the top, the more pressure on the left rod, and the top pops out.

not good at all.

I could glue the top, now that I think this gantry is messed up...


I have seen your bush mod and i will do it when i get a new gantry

the wood is slightly burned indeed... good, you can pretend it was laser cut LOL

 

If it's just the hole, you can reposition the rod and reform the hole with CA. Or fill the hole with a wood plug and redrill it. The later method, is what I am doing right now. Doesn't seem too hard.

 

Now that Mark mentions it. I did have a problem that I forgot about. One of my pex tubes ended up bent in the middle. And the result was the rod wasn't parallel, but tilted. You can check it by pressing the metal rod against the tube side. If it's bent you can't get it to lay flat against both ends at the same times, but it rocks when you press one side. I had to cut out the center wood around the pex. It sprung back straight, and I epoxied it back in that position.

-Kwok

 

Mark,

I am afraid I can't rotate the Z rods. Just too well glued.

I'm uploading 4 videos to youtube to show the wiggling
http://uk.youtube.com/jlbourdon77
Can you take a look?

How much for a full gantry set? (everything that moves along the Y axis minus the stepper: wood, 2 small rods, U screws + bolts, pex pipes, TNuts)

I plan to use bushing mod, and ZBF.

 

It looks like your Z-drive screw is bent, or the drive coupler has some serious offset. I changed mine back to one of these from McMaster-Carr (on page 1149), and it's smooth as glass now. The Lovejoy couplers were too unforgiving of axial offsets.

 

Further Help to Debug my Phlatty

I have to tilt the top part of the gantry forward to have the rods inserted. then the back lifts up.
I kind of ignored that so far, but now I look into this further, I think this is important.

The wobble is reduced when they are inserted , but still there.
THe further the Z gantry moved down, the more the rods are being pushed apart, and are pushing the top lid up, who then comes out even if I press it down with my hand

First, I do think like kwok: my rods are too short.

I've uplaoded to youtube a video of the short all thread rolling on a glass table. look straight to me
Just to ease debug I also reverted back to the original coupler.

The pex pipes do have quite some play around the rods too. Attached files

 

Dennis, I think you meant page 1161 in the McMaster catalog.

Yoram

 

JBourdon,

Is you z axis removable?
Did you enlarge your holes, by any chance?
Your top is not glued on, correct? It should really be screwed down. just redid mine and put 6 screws on mine. Here is a picture:

The rod are short, but I think that's not what is causing your problem. It's something wrong with your linear guides. But fyi , here is a picture I posted before at rcgroups. I overlaided the original rods and the new one's I made. You can see there is bearly any rod there to go into the hole:
Attached files

 

Kwok - My Z-rods were that short also, so I dropped a rubber o-ring in the bottom holes to "split the difference" between the top and bottom plates. That way, I have just over 1/8" support top and bottom, and it seems to work just fine.
btw, I used the o-rings because they were handy, and I thought it might reduce a little vibration noise. Did it??? Who knows, but it works anyway.

 

I think Mark designed them short, because he meant for them to be glued. And for people to put a nice dab of glue in the hole first. But if you make the top removable, it's really nice to have the full 1/4" length at the top. Mine fit , nice and tight, but still can be removed.

-Kwok

 

BTW guys, thanks for the help.ok, so now:

My Z axis top is removable, but as a single part.

Kwok, I don't understand how the screw wok. do they go in the sides of vertical panels?
I am afraid to split the wood if I do this. Could you post picts with top removed?
from zooming your picts, it looks like you added some extra wood.

I have used o-ring (metal though, but rubber is excellent idea) too but for my Y axis only.
I wished I had known this for the Z axis too.

I did not enlarged the holes. I am afraid to do such mod.

EDIT: good news: after some heavy persuasion, i managed to tip the rods out, with i think almost no damage... will work from there now.maybe not glue the rods?

EDIT2: the rods are not same diameter too: one is 0.40/0.41in, the other is 0.43.

 

No, I didn't screw into the vertical parts. I glued in some wood blocks. You really only need 4 screws ( the black one in my previous post). I didn't want to glue the two top pieces together (easier to get the rod out), so I added the two silver screws in the front. They are 1/2" long, so the end is flush and won't get hit by the Z Axis. Here are some pics:


Today, I am putting in the bushings for my Y axis. Just finished the top pair and they are so nice! Very low friction and no play at all. If you can verify/fix your rods, then you can just rip out the pex pipe and put in bushings. You will have to elongate the holes a little bit and glue in the bushings. I haven't done the Z Axis, because I might have to make a new one for my mod. 8 bushings are just $12 plus shipping from Mcmaster-Carr. Or if you need to replace the rods, you can buy whatever size you have locally (metric even).

-Kwok Attached files

 

Be careful when measuring rods, as a regular caliper or micrometer can lie to you about the functional "diameter". Imagine measuring a rod with a triangular cross-section. From a flat base to the opposite tip may measure 1.000000000", but the triangle will only fit inside a 1.33333333" diameter hole (if I remember my trigonometry correctly).
You really need a 3-sided rod gage (i.e. expensive) to measure round objects accurately, and then take the average of a multitude of readings.

 

I don't know if I agree with that, Dorsal. I understand your approach, but theory sometimes hinder. I bet if you just make multiple measurements, they would all be pretty consistent for each rod.

Hum, I missed what JBourdon wrote about the diameters. My original rods were 0.435". My new rods were 0.432" and that was enough to go from a tight impossible to move z-axis to a nice tight fit. You need to have a very nice tight fit, since it will be perfect after you apply some lube. So if the other rod was 0.41" or even 0.42", then that could mean a loose z-axis. Any play at all and the linear guide will fail to do it's job. That's the bad thing about the pex pipe, you need constant side pressure for it to work. I can't prove that such tiny variation matter. There just too many variables, but it's what I will believe until it is proven wrong.

For example, when I test fit my Y Axis with the pex pipe, I noticed a few things. It works ok on the Z axis because the rods are vertical; but not that well with the Y where the rods are horizontal, because of the force of gravity is perpendicular to the rods. All the weight **** on the top rod only. The bottom pex pipe didn't contact at all, so no pressure to stop sideways movement. Basically, it hangs on the top rod and can rock like a pendulum with the play on the bottom rod. A bushing would not allow that to happen, because it physically stops motion in all directions.

-Kwok

 

Hey all,

I've been working on the printer. Was difficult to gather enough time to allow me to do something meaningful right now...

I've taken a few picts, and made the following mods. It helps a lot. (also polished Z rods too, but not in picts)

I can even have the Z at 15inch/min while It was better at 10 before.

Mark, I think for now it will do. almost no more wobble.

I believe it will be difficult to debug by phone, even by webcam as the wobble is getting very small.
So let's cancel this week-end call.

I need more time cutting to see if it is still a problem.

JL Attached files

 

Only the outside edge of the rod touches. It needs to sit very tight against the pex tube. You can put a shim on the inside edge of the hole (maybe plastic container or bottle material, so the rod slips in easily) and force the 0.40 rod to sit further towards the outside edge.

 

Just a thought from watching the videos of your machine running.
Did you check your all thread to see if it is straight and not bowed?
That would induce a wobble like the one I noticed in the video.
While the rods not being straight could be a problem as well, Had you not said anything about what problem you were having, I would have suggested the Z all thread being bent right from the start.

 

there's a video of the allthread rolling on glas, and it's straight
thanks

I will delete the video of the wobble now.

 

I may be double covering something here but from looking at the videos including the one you made of the all thread being straight.....

It's not (IMHO) the all thread at all as far as being bent. It's just playing in the place holder hole the all thread goes into on the top. You can see the whole tool holder is wobbling in full 360 degrees. If you watch the video that’s showing the gantry from the side you can see the all thread playing around and around in the top place holding hole of the gantry.

A ¼” brass bushing would solve this issue provided this is the issue you having with the tool holder wobbling.

It wouldnt hurt removing the play on the linear rails/rods and plex pipe

Eric